The present invention relates to a semiconductor device and a method of manufacturing the same, and particularly to a semiconductor device in which a gate electrode is partly located over a buried insulating film and a method of manufacturing the same.
As a typical structure of a high-breakdown-voltage Laterally Diffused Metal Oxide Semiconductor (LDMOS) transistor, there is a REduced SURface Field (RESURF) MOS transistor (see Patent Document 1). To provide the LDMOS transistor with a higher breakdown voltage, it is necessary to uniformly extend a depletion layer in the drift region of a drain and, as a technique therefor, there is a field plate effect using a gate electrode layer.
The field plate effect is obtained by extending the gate electrode layer toward a drain over a semiconductor substrate, but a high electric field is formed under the drain-side edge of the gate electrode layer. Accordingly, in a typical structure, a thick oxide film is formed over a surface of the semiconductor substrate, and the drain-side edge of the gate electrode layer is positioned over the oxide film, thereby reducing the intensity of the electric field under the drain-side edge of the gate electrode layer.
As the thick oxide film described above, various oxide films are used depending on the generation of a process for forming the LDMOS transistor, but a Local Oxidation of Silicon (LOCOS) oxide film and a Shallow Trench Isolation (STI) are typically used. As the thick oxide film, a configuration using the STI is described in, e.g., Non-Patent Document 2.